K rather than Kc


Moderators: Chem_Mod, Chem_Admin

Jessa Maheras 4F
Posts: 121
Joined: Fri Aug 02, 2019 12:16 am

K rather than Kc

Postby Jessa Maheras 4F » Mon Feb 17, 2020 4:55 pm

In the book, it says that in order to use the Van't Hoff Eq for runs involving gases, you have to convert from K too Kc. What is the difference between the two terms?

Kishan Shah 2G
Posts: 132
Joined: Thu Jul 11, 2019 12:15 am

Re: K rather than Kc

Postby Kishan Shah 2G » Mon Feb 17, 2020 5:00 pm

This is a good question. When I was doing my calculations I used the same value for both but my calculations could be wrong. Does anyone know?

alicechien_4F
Posts: 104
Joined: Sat Jul 20, 2019 12:15 am

Re: K rather than Kc

Postby alicechien_4F » Mon Feb 17, 2020 11:58 pm

You have to convert from Kp to Kc because the values are different. I believe Kp and Kc are only the same when the number of moles of gas on the reactant and products sides are equal (correct me if I'm wrong!). Van't Hoff's equation relates Kc to change in temperature.

Julie_Reyes1B
Posts: 105
Joined: Sat Jul 20, 2019 12:16 am

Re: K rather than Kc

Postby Julie_Reyes1B » Tue Feb 18, 2020 12:02 am

In the book, K without a subscript refers to Kp, whereas in Dr. Lavelle's class, both terms will be identified using the subscripts.

Marni Kahn 1A
Posts: 107
Joined: Thu Jul 25, 2019 12:17 am
Been upvoted: 1 time

Re: K rather than Kc

Postby Marni Kahn 1A » Tue Feb 18, 2020 9:14 am

K is in terms of pressure, whereas Kc is in terms of concentration/molarity.

205405339
Posts: 77
Joined: Thu Jul 11, 2019 12:16 am

Re: K rather than Kc

Postby 205405339 » Tue Feb 18, 2020 9:37 am

K=(RT)^(change in n) x Kc

Robin Cadd 1D
Posts: 113
Joined: Thu Jul 11, 2019 12:16 am

Re: K rather than Kc

Postby Robin Cadd 1D » Tue Feb 18, 2020 11:07 am

Jessa Maheras 4F wrote:In the book, it says that in order to use the Van't Hoff Eq for runs involving gases, you have to convert from K too Kc. What is the difference between the two terms?


For gases, you automatically assume that K is Kp. Converting K to Kc is just converting K to Kp

Jessa Maheras 4F
Posts: 121
Joined: Fri Aug 02, 2019 12:16 am

Re: K rather than Kc

Postby Jessa Maheras 4F » Sun Mar 15, 2020 7:14 am

Julie_Reyes1B wrote:In the book, K without a subscript refers to Kp, whereas in Dr. Lavelle's class, both terms will be identified using the subscripts.


Thank you Julie that makes sense!!

Jessa Maheras 4F
Posts: 121
Joined: Fri Aug 02, 2019 12:16 am

Re: K rather than Kc

Postby Jessa Maheras 4F » Sun Mar 15, 2020 7:14 am

Robin Cadd 1D wrote:
Jessa Maheras 4F wrote:In the book, it says that in order to use the Van't Hoff Eq for runs involving gases, you have to convert from K too Kc. What is the difference between the two terms?


For gases, you automatically assume that K is Kp. Converting K to Kc is just converting K to Kp
Oh alright, thanks!

KHowe_1D
Posts: 103
Joined: Thu Jul 25, 2019 12:15 am
Been upvoted: 1 time

Re: K rather than Kc

Postby KHowe_1D » Sun Mar 15, 2020 7:16 am

Kp is in terms of pressure while Kc is in terms of molarity (concentration). I would say just during calculations to specify with the subscript.

Nawal Dandachi 1G
Posts: 102
Joined: Sat Sep 28, 2019 12:16 am

Re: K rather than Kc

Postby Nawal Dandachi 1G » Sun Mar 15, 2020 7:17 am

I always assume they are the same, but I guess when you are referring to gases, K is Kp, and Kp is not equal to Kc.


Return to “Van't Hoff Equation”

Who is online

Users browsing this forum: No registered users and 2 guests